A passive anti icing system for the engine cowl of the Global Hawk UAV was designed and evaluated under a NASA Phase I SBIR Program. The system utilizes five Loop Heat Pipes to remove 3.8 kW of waste heat from the hydraulic system and deliver it to the engine inlet during icing conditions. During non-icing conditions the heat is bypassed to relief valves on the fuel ullage tank to maintain their temperature above freezing. The system masses 18.5 kg and replaces some 15 lbs of existing equipment. A Phase II program to integrate the system aboard the aircraft is underway with the goal of starting flight tests in early 1999.